This invention relates in general to fluid line systems, and more particularly to a corrosion-resistant crimped joint between rigid metal tubing and flexible braided hose.
In automotive fluid systems, rigid tubing and flexible hose are interconnected to establish fluid pathways between remote system components. The hose is typically made of rubber or plastic, while the tubing is made of metal. To add strength to the hose, while maintaining its flexibility, the hose may be encased in a wire shell braided to a tubular form. Confronting ends of tubing and hose are typically coupled by means of a metal ferrule crimped at the joint of the hose/tubing interface.
FIGS. 1 and 2 depict a prior art coupling 10 between confronting ends of a rigid metal tube 12 and a flexible hose 14. Hose 14 has an inner layer 16 of a plastic material, such as teflon, and an outer layer 18 of a metal wire braid. Hose 14 is secured to tube 12 by means of a metal ferrule 20 crimped over hose 14 and tube 12 between a stop bump 22 and a containment bump 24 formed on tube 12. As can be seen in FIGS. 1 and 2, there is metal-to-metal contact between ferrule 20 and wire braid 18, and between ferrule 20 and tube 12 (at stop bump 22).
The metal-to-metal nature of the contact between ferrule 20 and the exteriors of tube 12 and hose 14 is desirable in that it creates a strong retention force between the ferrule, tube and hose. It is also problematic, however, in that it leads to formation of corrosion, particularly at the open ends of the ferrule 20 where exposure to the operating environment is greatest. Corrosion is a significant concern in automotive systems, as the operating environment routinely involves exposure to such elements as dirt, grime, moisture, fluids, salt, etc. Depending on the particular metallic materials utilized in coupling 10, galvanic reactions may also contribute to corrosion at the sites of metal-to-metal contact.
The present invention endeavors to reduce corrosion influx at crimp joints between rigid tubing and metal-braided flexible hose.